Field
This disclosure relates to servicing a wellbore. More specifically, it relates to methods of preventing formation damage from friction reducers.
Background
Natural resources such as gas, oil, and water residing in a subterranean formation or zone are usually recovered by drilling a wellbore down to the subterranean formation while circulating a drilling fluid in the wellbore. After terminating the circulation of the drilling fluid, a string of pipe, e.g., casing, is run in the wellbore. The drilling fluid is then usually circulated downward through the interior of the pipe and upward through the annulus, which is located between the exterior of the pipe and the walls of the wellbore. Next, primary cementing is typically performed whereby a cement slurry is placed in the annulus and permitted to set into a hard mass (i.e., sheath) to thereby attach the string of pipe to the walls of the wellbore and seal the annulus. Subsequent secondary cementing operations may also be performed.
Friction reducers are typically included in wellbore servicing fluids during pumping in order to minimize damage to the formation. Generally, friction reducers comprise aqueous solutions of a chemical additive which function to alter the fluid rheology by enhancing the viscosity and lowering the friction. When the chemical additive comprises a polymer, e.g., polyacrylamide, the polymer could, over a period of time degrade. For example, degradation of the polymer may occur by hydrolysis of the polymer resulting in charged compounds that can be neutralized by the formation of a salt. These salts of polymeric origin tend to form polymer-cation aggregates in the presence of multivalent cations such as calcium, magnesium, or aluminum. These polymer-cation aggregates will grow in size over time and can clog surface equipment, piping, and potentially cause pore closure in downhole formations. Thus, an ongoing need exists for friction reducers having a reduced tendency to form such aggregates.